Adjusting device for gas exchange valves

ABSTRACT

An improved adjusting device for an electromagnetically-actuated, spring-loaded positioning system in displacement engines, such as for lifting gas exchange valves in internal combustion engines. The adjusting device comprises a spring system and two electrically-operated, opposed actuating solenoids, by means of which an anchor plate may be moved therebetween, and held at two distinct positions corresponding to an open and closed position of the gas exchange valve. The fast switching time behavior of the anchor plate is assisted by selectively distributing a ferromagnetic material in a casing (sleeve) around the gap between the two electromagnets. In the preferred embodiment, the effective magnetism of each pole surface is increased by providing the casing with a plurality of holes along its mid-section. This corresponds to the neutral or dead point of the spring system and anchor plate travel between the two electromagnets. Alternate embodiments include: (1) the continuous or stepwise reduction in wall thickness of the casing from its ends to its midpoint; and (2) selectively gradient doping a uniformly thick casing wall with a ferromagnetic material such that the magnetism adjacent each pole surface is increased. The entire adjusting device is easily constructed using currently available solenoid actuators and spring systems.

FIELD

The invention is directed to an improved adjusting device for gasexchange valves in displacement engines of the type employingelectromechanically-actuated, spring-biased reciprocating actuators,such as are commonly used for lifting valves of internal combustionengines. More particularly, the invention relates to improved fastswitching time behavior between the open and closed positions of gasexchange valves in an internal combustion engine whereby a pair ofopposed electromagnetic devices are alternately excited thus attractinga reciprocating spring-biased anchor plate back and forth therebetween.The anchor plate is linked to the rod end of the gas exchange valve suchthat the engagement of the anchor plate with a pole surface associatedwith either electromagnet corresponds to either an open or closedposition of the gas exchange valve.

BACKGROUND

A similar type of valve adjusting device is known in principal fromDE-OS 30 24 109 corresponding to U.S. Pat. No. 4,455,543 (Pischinger etal).

This known device shows a gas exchange valve for an internal combustionengine, the stem of which is joined to the valve disk and has an anchor(or armature) plate which is alternatingly attracted to two opposedactuating solenoids, causing the valve to open or close. Pischinger alsodiscloses the use of a distance spacer and a magnet cover (collectivelyknown in the art as a "casing") which function to affix the tappedwinding coils or solenoids and the bias coil within the cylinder head.

Modern day internal combustion engines have made great strides in valvedesign. The improved valve mechanisms have resulted in improved poweroutput and fuel efficiency, and have also reduced emissions. This inlarge part is due to improvements in valve timing through the use ofsolenoid and spring-biased valve actuator assemblies. The prior artmethods for improving gas exchange valve switching behavior have beenprimarily directed to ensuring reliable switching behavior by improvingvalve stem alignment within the actuator assembly. While this is astarting point for improving valve switching behavior, there is still aneed for increasing the speed of the fast switching time behavior of theanchor plate to ensure precise position changes, and to keep up with theinterval demands that are placed on gas exchange valves by newer enginedesigns under normal operating RPM ranges.

One method for accomplishing this is by increasing the magnetic forceassociated with each electromagnet in order to attract the reciprocatinganchor plate. However, this also requires the use of stronger springs inorder to compensate for the increased lag time associated with astronger decaying electromagnetic force upon deenergization of anassociated solenoid. This is not a preferred way of achieving fasterswitching behavior as larger magnetic cores and springs defeat thepurpose of designing small and conveniently sized actuator assemblies.Moreover, the reliability of the reciprocating movement of the anchorplate must also be assured. Unduly powerful electromagnetic forces willtend to result in undesirable switching behavior as the associatedspring members become fatigued and weakened over long operating periods.

Thus, there is a definite need in the art to improve the speed of fastswitching time behavior of gas exchange valves whereby such improvementsmake optimal use of readily available components associated with currentstate of the art valve actuator designs.

THE INVENTION OBJECTS

It is among the objects of the invention to provide an improved solenoidactuated gas exchange valve device having the properties of more rapidfast switching time behavior and reliable movement of the anchor platedevice;

It is another object of this invention to provide an improved actuatorassembly wherein the high speed or fast switching time behavior of theanchor plate is improved by increasing the effective magnetism of eachpole surface of a pair of opposed electromagnets without using largeriron cores;

It is another object of the invention to provide an improved valveactuator system whereby a ferromagnetic casing is provided as a guidemember for the reciprocable anchor plate and the casing is selectivelysized in cross section to promote the switching speed and behavior ofthe anchor plate;

It is another object of the invention to provide an improved valveactuator system whereby the effective magnetism of each pole surface ofa pair of opposed electromagnets is increased by providing a casing as aguide member for the reciprocating anchor plate wherein the casing isselectively doped with a ferromagnetic material so that the fast timeswitching speed and behavior of the anchor plate is increased and;

Still other objects will be evident from the following specification,drawings and claims.

DRAWINGS

FIG. 1 shows a side elevation, cross-section view of the improvedactuator adjusting device of this invention.

FIG. 2 shows a fragmentary, cross-sectional view of an alternateembodiment for the adjusting device of this invention.

FIG. 3 shows a fragmentary, cross-section view of a second alternateembodiment for the improved adjusting device of this invention.

SUMMARY

I have found that the fast switching time behavior of electromagnetic,spring-biased adjusting devices for gas exchange valves in internalcombustion engines may be improved by providing an additional magneticforce to assist the movement of the reciprocating anchor plateassociated with these adjusting devices. This may be accomplished byselectively distributing an amount of ferromagnetic material surroundingthe pathway of the reciprocating anchor plate.

In the preferred embodiment a casing is provided to surround theactuator assembly. The casing resembles a cylindrical mantle or sleevewhich forms an enclosure about the space or gap between the opposedelectromagnet cores. This gap is the region where the anchor plate isalternately reciprocated between opposing electromagnet cores and isdisposed to engage a pole surface of each electromagnet core as itbecomes energized. This reciprocating movement corresponds to the movingof an associated gas exchange valve from a closed to an opened positionor vice-versa.

In the preferred embodiment the casing (sleeve) contains a uniformdegree (distribution therein) of ferromagnetic material, and is providedwith holes or relieved portions along its central region adjacent thegap corresponding to the neutral or locus point of the spring system. Inother words, the surrounding ferromagnetism provided by the casingacting on the actuator is significantly reduced in the region of themantle sleeve corresponding to where the anchor plate approaches itsmid-point of travel between the two opposed electromagnets. It has beenfound that this variable degree (gradient) of lateral outward-attractingmagnetic force promotes faster time switching behavior of the anchorplate in its direction of travel towards a pole surface of anelectromagnet. This increases the effective magnetism associated witheach electromagnet so that the anchor plate is quickly attracted to theaffected pole surface upon energization of that electromagnet, since theferromagnetic material concentration in the surrounding casing/mantle isgreatest in the end regions of the mantle adjacent the pole surfaces ofthe opposed electromagnets.

An alternate embodiment for selectively distributing the ferromagnetismof the casing wall comprises a continuous reduction in thickness in thecasing wall from its outer end regions adjacent each pole surfacetowards its mid-point region adjacent the neutral or dead point of theanchor plate travel. A second alternate embodiment includes a stepwisereduction in the outer wall thickness of the casing similar to thecontinuous reduction in wall casing embodiment.

A third alternate embodiment of the casing wall includes a uniformlythick wall that is selectively doped with ferromagnetic material. Thedistribution of the doping is most heavily concentrated at the outerends of the casing adjacent the pole surfaces of each electromagnet anddecreases significantly towards the mid-point of the casing, so there isa doping gradient decrease from the outer ends toward the middle.

In all embodiments the inner cylindrical wall of the casing (i.e., thewall surface directly adjacent the reciprocating anchor plate) is smoothto permit unobstructed reciprocating travel of the anchor platetherewithin.

DETAILED DESCRIPTION OF THE BEST MODE

The following detailed description illustrates the invention by way ofexample, not by way of limitation of the principles of the invention.This description will clearly enable one skilled in the art to make anduse the invention, and describes several embodiments, adaptations,variations, alternatives and uses of the invention, including what Ipresently believe is the best mode of carrying out the invention.

FIG. 1 illustrates an isolated view of an adjusting device for a gasexchange valve of the type normally found within the engine block of aninternal combustion engine. The adjusting device comprises opposingshielded electromagnetics or iron cores 10 and 14. Each electromagnet isgenerally U-shaped in cross-section to form a cup magnet and has coilsor solenoids 12 and 16 annularly installed therein. The solenoids 12, 16are aligned parallel to the axis of the annulus coinciding with the axisof valve stem 24. Solenoid 12 is associated with electromagnet 10 andsolenoid 16 is associated with electromagnet 14. Each electromagnet 10and 14 also has associated therewith pole surfaces 36 and 38,respectively. An anchor plate 18, being reciprocable in the verticaldirection (as seen in FIG. 1), is provided, and it moves back and forthbetween each pole surface 36 and 38. The anchor plate 18 also hasattached thereto a stem 30 which is disposed to engage the stamp portion24 of a valve stem associated with a gas exchange valve disc (disc notshown).

As there is no theoretical difference between intake and exhaust valveconstruction, the following discussion is generic to both types of gasexchange valves.

During the period that the excitement of solenoid 16 is caused to occur,anchor plate 18 is attracted towards pole surface 38 which results inthe downward depression of stamp portion 24 and hence moves the gasexchange valve to the open position. Conversely, as anchor plate 18 isattracted by pole surface 36 (i.e., when solenoid 16 is de-energized andsolenoid 12 is excited) then the gas exchange valve is moved to theclosed position.

Upper and lower coil springs 20 and 28, respectively, being coalignedwith the central axis of the valve stem, are provided to bias the anchorplate 18 towards the opposing pole surface of the associatedelectromagnet. As is seen in FIG. 1, coil spring 20 is constrained atits upper end by top abutment 22 and is disposed to be inserted in andreceived by a relieved central portion in the stem 30 at its bottom end.In a similar fashion, lower coil spring 28 abuts the top flanged surface24a of stamp portion 24 of the valve stem at its top end and engageslower abutment 26 at its bottom end. When the electromagnets 10 or 14are not excited, the neutral or dead center (locus) position of thespring system is about in the middle, that is, such that the anchorplate 18 comes to rest in the middle between the two pole surfaces 36and 38. For more details on valve actuator assemblies directed toprecise and simple adjustment of the valve stroke see my earlier issuedU.S. Pat. No. 4,719,882.

In operation, only one of the solenoids 12 or 16 is excited (energized)at any one time. As upper solenoid 12 is energized, anchor plate 18 isattracted towards pole surface 36 which results in the compression ofcoil spring 20. As solenoid 12 is de-energized and the flow of currentthrough electromagnet 10 is shut off, the spring force of compressedspring 20 overcomes the now decaying electromagnetic force attractingpole surface 36 to the upper surface of anchor plate 18 and anchor plate18 is moved to a position near the opposing electromagnet 14 where itwill be caught by a catch current associated with the energizing of theopposing solenoid 16.

The area between the opposing pole surfaces 36 and 38 is enclosed by thecasing 32. In the preferred embodiment, the shape of the casing 32 is inthe form of a cylindrical mantle or sleeve and is constructed of aferromagnetic material in order to assist in the magnetic attraction ofthe anchor plate 18 in its direction of travel towards a pole surface ofan energized electromagnet.

A plurality of holes or relieved portions 34 are provided along casing32 to encourage the switching behavior of the anchor plate 18 during theabove-described periods of alternately excited solenoid action. In thepreferred embodiment, the casing 32 has an even distribution offerromagnetic properties throughout its construction. By placing holes34 selectively about its mid-portion, the distribution of ferromagneticproperties of casing 34 are greater towards its upper and lower edgeregions adjacent the pole surfaces 36 and 38, respectively, and thus,effectively increases the magnetic attraction associated with each polesurface.

While the preferred embodiment discloses the holes 34 as through holesin the sidewall of casing 32, it is understood that other derivations ofthe preferred embodiment may also result in a smaller ferromagneticproperties of the casing 32 about its mid-section, including but notlimited to forming relieved portions that do not extend clear throughthe thickness of the casing 32 or by a substitution of numerous pits inthis region instead of the holes 34.

ALTERNATE EMBODIMENTS

Alternate embodiments for the construction of casing 32 are shown inFIGS. 2 and 3. For clarification in this description, the index numbersin FIGS. 2 and 3 refer to the same items as in FIG. 1.

As is best seen in FIG. 2, the casing 32 does not have a uniformcross-sectional thickness, but instead has a smoothly decreasingthickness from its upper and lower end to the midpoint of the casing 32.This corresponds to the neutral or dead center of the anchor plate whenthe actuating valve assembly is in a rest position. It is understoodthat although the changes in wall thickness are shown as continuous(i.e., a smoothly decreasing thickness of the casing) it is noted that astepwise decrease towards the central region is also possible and may bepreferable from a construction standpoint.

In the embodiment of FIG. 3, no overall annular thickness changes orcutouts are made to the wall thickness of casing 32. Instead, thematerial composition of the wall is selectively altered. In thisembodiment, the material composition adjacent the upper and lowerregions of casing 32 is doped to provide a gradient with a greaterdegree of ferromagnetic material than is provided to the central region.As described above, this increases the effective magnetism associatedwith each energized electromagnet and thus encourages the fast switchingtime behavior of the anchor plate 10 from one pole surface to the other.

The design aspects disclosed in FIGS. 1-3 may be combined with eachother to form several combinations which achieve the same results offaster switching behavior. For example, the additional holes 34 of FIG.1 may be combined with the varying wall thickness of FIG. 2 or with thedisproportionately (gradient) doped casing 32 of FIG. 3. Likewise, thedisproportionately doped casing of FIG. 2 may be combined with the holes34 of FIG. 1. From the above description it is obvious that othercombinations are possible, but for the sake of brevity will not bementioned here.

It should be understood that various modifications within the scope ofthis invention can be made by one of ordinary skill in the art withoutdeparting from the spirit thereof. I therefore wish my invention to bedefined by the scope of the appended claims as broadly as the prior artwill permit, and in view of the specification if need be.

I claim:
 1. An improved electromagnetically operated, spring-biasedactuator assembly for gas exchange valves in internal combustionengines, comprising in operative combination:a) a first actuatingsolenoid and a second actuating solenoid, said second actuating solenoiddisposed opposite to and spaced from said first actuating solenoid asufficient distance to define a gap therebetween, both of said solenoidshaving a ferromagnetic iron core; b) means for reciprocatingly actuatinga gas exchange valve, said gas exchange valve being movable between afirst, closed operating position to a second, open operating position;c) said reciprocating actuator means including a generally disc-shapedanchor plate having a central axis and a peripheral edge spacedoutwardly from said axis, said anchor plate disposed to travel betweensaid actuating solenoids and selectively attractable to and guidinglyreciprocated between positions of engagement with a pole surface of eachof said actuating solenoids, said first actuating solenoid pole surfaceengagement position corresponding to said closed operating position ofsaid gas exchange valve, and said second actuating solenoid pole surfaceengagement position corresponding to said open operating position ofsaid gas exchange valve; d) said anchor plate including:i) an upper andlower guide stem, each of said guide stems disposed opposite one anotherand coaxial with the axial center of said anchor plate, ii) said upperguide stem being receivingly engageable by a central axial bore of saidfirst actuating solenoid and said lower guide stem being receivinglyengageable by a central axial bore of said second actuating solenoid;ii) said lower guide stem including means for contacting a coaxiallyaligned stamp member of a gas exchange valve stem to transferreciprocating movement of said anchor plate to said gas exchange valve;e) a spring system for symmetrically stressing said anchor plate andassisting said reciprocating movement upon the appropriate excitation ofeither of said actuating solenoids; f) means for improving the switchingbehavior of said actuator assembly in association with said gap so thatthe fast time switching of said anchor plate is increased while precisemovement between said closed and open operating positions of said anchorplate is maintained.
 2. An actuator assembly for gas exchange valves asin claim 1 wherein said means for improving the switching behaviorincludes:a) a ferromagnetic perimeter casing member disposed surroundingsaid anchor plate peripheral edge and bridging said gap; and b) saidcasing member having a gradient of attractive magnetic force whichincreases the effective magnetism of the pole surfaces of each of saidadjusting solenoids.
 3. An actuator assembly for gas exchange valves asin claim 2 wherein:a) said casing member is a sleeve which has asubstantially uniform thickness; and spaced end portions overlapping thepole surface of each of said actuating solenoids; and b) said casingsleeve includes a plurality of holes disposed medially of saidoverlapping end portions.
 4. An actuator assembly for gas exchangevalves as in claim 2 wherein said casing has a wall thickness which isthinner at its middle than at said overlapping end portions.
 5. Anactuator assembly for gas exchange valves as in claim 1 wherein saidmeans for improving the switching behavior includes:a) a perimetercasing sleeve disposed adjacent said gap and having overlapping endportions extending beyond the pole surfaces of each of said actuatingsolenoids; b) said casing sleeve is selectively doped with ferromagneticmaterial in a gradient distribution to increase the effective magnetismof the pole surfaces of each of said adjusting solenoids.